Human mass balance, metabolism, and cytochrome P450 phenotyping of lusutrombopag

Figures & data

Figure 1. Chemical structure of [¹⁴C]-lusutrombopag, with the site of the ¹⁴C label indicated (*).

Figure 2. Mean concentration-time profiles of radioactivity in plasma and whole blood and lusutrombopag and M5 in plasma after a single oral administration of 2 mg of [¹⁴C]-lusutrombopag to healthy subjects. Each point represents the mean from seven subjects. All M3 concentrations were below the limit of quantitation.

Table 1. Pharmacokinetic parameters of lusutrombopag and M5 and total radioactivity in plasma and whole blood after a single oral administration of 2 mg of [¹⁴C]-lusutromobpag.

	Total radioactivity		Plasma
Parameters	Whole blood	Plasma	Lusutrombopag	M5
AUC0-∞ (ng Eq·h/g or ng·h/mL)	1950 (23.9)	3370 (24.7)	1880 (30.1)	ND^a
AUC0-t (ng Eq·h/g or ng·h/mL)	NC	3000 (26.1)	1870 (29.6)	4.51 (68.6)
Cmax (ng Eq/g or ng/mL)	44.1 (23.3)	82.8 (22.6)	66.2 (25.6)	0.461 (27.4)
tmax (h)^b	5.00 (4.00–8.00)	5.00 (5.00–8.00)	5.00 (4.00–10.00)	5.00 (5.00–8.00)
t1/2 (h)	111 (14.9)	70.7 (20.2)	25.7 (6.9)	ND^a
CL/F (L/h)	1.04 (24.0)	0.597 (24.6)	1.07 (29.9)	NA

All values except for t_max represent the geometric mean (CV%) of all subjects.

^aTerminal rate constant of M5 was estimable for only 1 of the 7 subjects.

^bMedian and range are presented.

NA: not applicable; NC: not calculated; ND: not determined; ng Eq: ng [¹⁴C]-lusutrombpag equivalent; C_max: maximum concentration; t_max: time of maximum concentration; t_1/2: apparent terminal half-life; AUC_0-t: area under the concentration-time curve from time zero up to the last quantifiable concentration; AUC_0-∞: area under the concentration-time curve from time zero to infinity; CL/F: apparent total clearance.

Figure 3. Representative HPLC-radiochromatograms of plasma collected from 8 h, urine collected from 0 to 216 h, and feces collected from 0 to 336 h after single oral administration of 2 mg of [¹⁴C]-lusutrombopag to healthy subjects.

Figure 4. Postulated metabolic pathways of lusutrombopag in humans.

Table 2. Composition of lusutrombopag and its metabolites in urine and feces after a single oral administration of 2 mg of [¹⁴C]-lusutromobopag, and assignment of MS/MS fragmentations of unidentified metabolites.

	RT	[M + H]^+		% of dose excreted
Metabolite	(min)	(m/z)	Estimated fragmentation	Urine^a	Feces^a
Lusutrombopag	75.6	591		0.06	16.2
M1 (acyl glucuronide)	70.3	767		0.02	1.59
M2 (taurine conjugate of β-oxidated carboxylic acid)	59.9	700		ND	0.66
M3 (5-keto)	58.1	605		ND	2.04
M4 (β-oxidated carboxylic acid)	41.3	593		ND	1.53
M5 (O-deshexyl)	35.2	507		0.03 (M5)	17.93 (M5 and M6)
M6 (O-propanol or O-acetic acid)	36.2	565		ND
M7 (O-ethane-1,2-diol)	37	567		ND	16.86
Total (including other unknown metabolites)				1.07	83.13

ND: not detected; RT: retention time.

^aValues represent the mean of all subjects.

Table 3. In vitro metabolism of [¹⁴C]-lusutrombopag by recombinant human cDNA expressed CYP enzymes.

Enzyme	Formation rate of lusutrombopag-6-hydroxy (fmol/h/pmol P450)
Control	21.2
CYP1A2	29.6
CYP2C9	92.6
CYP2C19	591
CYP2D6	82.7
CYP3A4	78.3
CYP4A11	143
CYP4F2	34.5

The control study was conducted with control supersomes and the amount of control supersomes was equal to that of other CYP supersomes.

Table 4. Effect of P450 chemical inhibitors on the formation of lusutrombopag-6-hydroxy from [¹⁴C]-lusutrombopag following incubation with human liver microsomes.

Inhibitor (associated CYP)	Formation rate of lusutrombopag 6 hydroxy (pmol/h/mg protein)	% inhibition from control
Control	40.1, 46.6*	–
α-Naphthoflavone (CYP1A2)	36.5	8.93
Sulfaphenazole (CYP2C9)	43.3*	7.03*
Ticlopidine (CYP2C19)	31.9	20.3
Quinidine (CYP2D6)	35.2	12.1
Ketoconazole (CYP3A4)	21.6	46.0
HET0016 (CYP4)	16.8	58.2

*The inhibition study for CYP 2C9 using sulfaphenazole was performed separately.

Table 5. Effect of P450 chemical inhibitors on the formation of lusutrombopag-6-hydroxy and lusutrombopa-β-oxidated carboxylic acid from [¹⁴C]-lusutrombopag following incubation with cryopreserved human hepatocytes.

Inhibitor (associated CYP)	Formation rate (pmol/h/1 × 10^6 cells)		% inhibition from control
	Lusutrombopag-6-hydroxy	Lusutrombopag-β-oxidated carboxylic acid	Lusutrombopag -6-hydroxy	Lusutrombopag-β-oxidated carboxylic acid
Control	2.19, 1.99*	2.25, 2.04*	–	–
α-Naphthoflavone (CYP1A2)	1.97*	2.00*	1.17*	2.37*
Sulfaphenazole (CYP2C9)	2.08	2.18	4.89	3.05
Ticlopidine (CYP2C19)	2.03	2.24	7.17	0.534
Quinidine (CYP2D6)	1.86*	2.16*	6.72*	−5.68*
Ketoconazole (CYP3A4)	1.85	1.71	15.7	24.2
HET0016 (CYP4)	0.499	0.947	77.2	57.9

*The inhibition study for CYP 1A2 and 2D6 using α-naphthoflavone and quinidine were performed separately.